Did you move into a new home with a mysterious furnace? Is your current furnace or boiler struggling with poor performance? Knowing how old your HVAC heating equipment is can help you decide between further maintenance or replacement.

After all, furnace age impacts energy efficiency, indoor air quality, and even the purchase price of a home. For homeowners, an old furnace is a ticking time bomb; replacing it is always a matter of when not if.  

How to Determine the Age of a Furnace by Serial Number 

So yes, knowing the age of your furnace or boiler is very helpful when making big decisions about a possible upgrade.

The good news is that in most cases, you can use the furnace model number or serial number to determine the year your furnace or boiler was made. HVAC manufacturers use the first four digits of the furnace, boiler, or AC unit’s serial number to indicate when the equipment was made.

While newer furnaces have the manufacture date noted conveniently on the side (called the furnace label), old furnaces usually take a bit more digging to find the serial number.

Here’s where to find the serial number on your furnace:

  1. Remove the small door on the front of your furnace. In some cases, a sticker with the manufacture date will be on the inside of the door.
  2. Turn off the furnace and look at the fan blades. Some manufacturers stamped the date on the fan.

Once you’ve found the serial number, examine the first four digits. For example, a furnace or boiler serial number that starts with 0188 was most likely made in January 1988.

How Do I Know How Old My Furnace Is If I Can’t Find the Serial Number? 

No luck finding the serial number? You might be able to use the furnace model number, usually found in the same places you’d find the serial number – some manufacturers treat these numbers interchangeably.

Decoding Furnace Model Numbers

Sometimes you can find the age of your furnace by looking at the nine-digit furnace model number. In most cases, the first character is a letter. The second and third numbers might be the year, and the fourth and fifth numbers might denote the week of the year the unit was made.

Further good news is that most manufacturers have a furnace model number lookup that lets you determine furnace age by serial number, the model name, or other defining features of the system.

You can even contact the furnace manufacturer. They may be able to determine the model and approximate age by photos or other identification methods.

Related Content: What Is More Expensive, Heating or Cooling?

Does the Age of My Furnace Affect Energy Efficiency? 

Yes! Even top-of-the-line HVAC equipment made a decade or more ago has a weak spot: energy efficiency. Furnaces were less efficient ten to fifteen years ago, and your old gas furnace is costing you more to operate than new a modern system would.

Newer Energy Star®-rated furnaces or air-exchange heat pumps require less energy to maintain the same temperatures. Older systems operate at roughly 56-70% efficiency, with more modern furnaces being up to 98.5% efficient and heat pumps being 300% efficient.

Even though it’s triple the energy efficiency of a gas furnace, a heat pump might not save you on heating costs if your current furnace is natural gas, which is very inexpensive compared to electricity. But if the heat pump has a higher SEER than your current air conditioner, it will save you money during the summer when it acts as your state-of-the-art air conditioner.

Replacing your gas furnace with a heat pump also vastly reduces your home’s carbon footprint and eliminates its risk as a source of carbon monoxide poisoning. Rural homeowners who replace their propane or heating oil furnaces or boilers with an electric heat pump will bring both their heating and air conditioning bills down immediately.

So, When Is It Time to Replace a Furnace?

While it may not make financial sense to replace an old furnace that’s still working, it should inform your decision to fix it when problems arise.

If you’re debating when to replace your furnace, keep these points in mind:

  • The cost of one-time or recurring repairs compared to heating system replacement.
  • The expected energy savings from upgrading to an electric heating system or heat pump.
  • The average lifespan of gas or electric heating systems.
  • Seasonal needs, such as waiting to replace the unit until next fall when it will be needed.

You can always count on your local One Hour Heating & Air Conditioning® technician to provide honest, reliable recommendations about when it’s time to replace a furnace or if it’s best to repair your existing unit.

Make a Smart HVAC Decision with Professional Insight 

Can’t figure out how old your furnace is? It’s not always easy! Take the guesswork out with One Hour Heating & Air Conditioning®. Our reliable technicians will evaluate your heating equipment and help you determine if an energy efficiency upgrade makes sense.

Heating is expensive – and a new furnace or heat pump is an investment. To get the help you need to make the right decision, find the One Hour® location near you or call (800) 893-3523 today.